> On Oct 16, 2017, at 1:05 PM, Xiaodi Wu <xiaodi...@gmail.com> wrote: > > > On Mon, Oct 16, 2017 at 10:49 Jonathan Hull <jh...@gbis.com > <mailto:jh...@gbis.com>> wrote: > >> On Oct 16, 2017, at 7:20 AM, Xiaodi Wu <xiaodi...@gmail.com >> <mailto:xiaodi...@gmail.com>> wrote: >> >> To start with, the one you gave as an example at the beginning of this >> discussion: Two sets with identical elements which have different internal >> storage and thus give different orderings as sequences. You yourself have >> argued that the confusion around this is enough of a problem that we need to >> make a source-breaking change (renaming it) to warn people that the results >> of the ‘elementsEqual’ algorithm are undefined for sets and dictionaries. >> >> No, I am arguing that the confusion about ‘elementsEqual’ is foremost a >> problem with its name; the result of this operation is not at all undefined >> for two sets but actually clearly defined: it returns true if two sets have >> the same elements in the same iteration order, which is a publicly >> observable behavior of sets (likewise dictionaries). > > But that iteration order is undefined and could easily change due to changes > in the private/internal structure of sets/dictionaries. Algorithms that rely > on that “publicly observable behavior” (i.e. leaking of internals) will > suddenly break. > > And an algorithm in which such “sudden breakage” would occur is…?
Here are a few off the top of my head: func hasPrefix(Sequence)->Bool func hasSuffix(Sequence)->Bool func containsSubsequence(Sequence)->Bool What do these methods mean with regards to Set’s “publicly observable behavior”? > > You keep claiming that this bug is a feature because it is the current > behavior… but that is tautological reasoning. > > Thanks, > Jon
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